In the manufacture of semiconductor devices, ion implantation is used to dope semiconductors with impurities. Ion implantation systems are often utilized to dope a workpiece, such as a semiconductor wafer, with ions from an ion beam, in order to either produce n- or p-type material doping, or to form passivation layers during fabrication of an integrated circuit. When used for doping semiconductor wafers, the ion implantation system injects a selected ion species into the workpiece to produce the desired extrinsic material.
It is often desirable to determine the amount of dopant being delivered to the workpiece in the ion implantation. The measurement of ions implanted in a wafer or workpiece is referred to as dosimetry. In ion implantation applications, dosimetry is typically performed by measuring electrical current (e.g., the ion beam current). In controlling the dosage of implanted ions, closed loop feedback control systems are commonly utilized to dynamically adjust the implantation in order to achieve dose uniformity in the implanted workpiece. Such control systems monitor a current of the ion beam in order to control a speed at which the workpiece is scanned through the ion beam, therein providing a uniform implantation of ions across the workpiece.
In ion implantation systems having a ribbon-shaped ion beam (e.g., an electrostatically scanned ion beam having a cross-sectional width greater its height), a profile, or shape, of the ion beam is often desired in order to properly tune the translation speed and path of the workpiece through the beam to achieve uniform doping. In such a circumstance, the Faraday cup is typically translated or scanned through the ion beam while the ion beam is electrostatically scanned at the same frequency as utilized during implantation into a workpiece. As such, a slit in the Faraday cup incrementally measures beam current associated with the ion beam and the Faraday cup will dwell at each spatial point long enough to integrate the current over a full beam profile.
Such a passing of the Faraday cup through the ion beam provides a time-dependent profile of the ion beam, and is typically considered to be an adequate approximation of the overall profile of the ion beam. However, since the time-dependent profile is typically performed using the same frequency of scanning of the ion beam utilized during actual implantation into a workpiece, and since more than one profile is often desired to reduce noise effects, excessively long profiling times are commonplace, and throughput is compromised.